Is Stem Cell Therapy the Future of Orthopedics?

( Hua Feng ) 대한슬관절학회 2018 대한슬관절학회지 Vol.30 No.3

Recursive Least-squares Estimation for Multivariable Systems Based on the Maximum Likelihood Principle

Huafeng Xia,Yongqing Yang,Feng Ding 제어·로봇·시스템학회 2020 International Journal of Control, Automation, and Vol.18 No.2

This paper studies the identification problem of multivariable controlled autoregressive moving average systems. For the case with a parameter matrix and an unmeasurable vector in the system identification model, we transform the model into several submodels based on the number of the outputs. A maximum likelihood-based recursive least-squares algorithm is derived to identify the parameters of each submodel. A multivariable recursive extended least-squares algorithm is provided as a comparison. The effectiveness of the proposed identification algorithm is verified by simulation examples.

Iterative Algorithm for Feedback Nonlinear Systems by Using the Maximum Likelihood Principle

Huafeng Xia 제어·로봇·시스템학회 2024 International Journal of Control, Automation, and Vol.22 No.4

This paper aims to find a maximum likelihood least squares-based iterative algorithm to solve the identification issues of closed-loop input nonlinear equation-error systems. By adopting the key term separation technique, the parameters of the forward channel are identified separately from the parameters of the feedback channel to address the cross-product terms. The hierarchical identification principle is introduced to decompose the original system into two subsystems for reduced computational complexity. The iterative estimation theory and the maximum likelihood principle are applied to design a new least-squares algorithm with high estimation accuracy by taking full use of all the measured input-output data at each iterative computation. Compared with the recursive least-squares (RELS) method. The simulation results verify theoretical findings, and the proposed algorithm can generate more accurate parameter estimates than the RELS algorithm.

Maximum Likelihood-based Multi-innovation Stochastic Gradient Method for Multivariable Systems

Huafeng Xia,Yan Ji,Yanjun Liu,Ling Xu 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.3

This paper considers the parameter estimation problems for multivariable controlled autoregressive moving average systems. By means of the decomposition technique, a multivariable system is transformed into several identification submodels according to the number of outputs. A maximum likelihood extended stochastic gradient identification algorithm is derived for identifying each subsystem by using the maximum likelihood principle. In order to improve the convergence rate, a multivariable maximum likelihood-based muti-innovation stochastic gradient algorithm is proposed. The proposed algorithms can generate more accurate parameter estimates compared with the multivariable extended stochastic gradient algorithm. The illustrative simulation results show that the proposed methods work well.

Distributed Fixed-time Formation-containment Control for Multiple Euler-Lagrange Systems with Directed Graphs

Menghu Hua,Huafeng Ding,Xiang-Yu Yao,Xinxin Zhang 제어·로봇·시스템학회 2021 International Journal of Control, Automation, and Vol.19 No.2

In this paper, the distributed fixed-time formation-containment (DFTFC) problem of multiple EulerLagrange systems with parametric uncertainties and input disturbances is studied under directed graphs. First, a distributed fixed-time sliding-mode estimator is constructed to estimate the desired states of each robot with that only parts of followers can access the information of leaders. Next, based on the estimator, a distributed fixed-time formation control algorithm is developed to drive leaders to achieve a specified formation. Then, the distributed fixed-time containment control algorithm is proposed for followers with its estimated states being tracked in a fixed time. Note that an explicit upper bound of the convergence time of DFTFC control algorithm is obtained independent of initial conditions. Finally, numerical simulations are performed to show the effectiveness of the obtained theoretical results.

Preparation and enzymatic activity of Fe3O4-IDA-Ni/NAD kinase magnetic catalyst

Changxia Liu,Yadi Yang,Huafeng Gao,Xiaoshuang Bai,Zheng-Jun Li 한국화학공학회 2020 Korean Journal of Chemical Engineering Vol.37 No.3

The use of oxidoreductases as biocatalysts for industrial production of valuable compounds has a strong demand for NADP. Herein, we prepared superparamagnetic NAD kinase catalyst to synthesize NADP in vitro. First, Fe3O4 particles were synthesized through a solvothermal method, followed by the chemical modification with epichlorohydrin, iminodiacetic acid, and Ni2+ to yield functional Fe3O4 sub-microspheres. Subsequently, NAD kinase of Escherichia coli was overexpressed and immobilized on to the surface of magnetic sub-microspheres. The immobilized NAD kinase was used to catalyze the conversion of NAD to NADP in a cell-free system. Under optimal condition, the conversion ratio of NAD reached 91.7% and remained at 86.3% after repeated use for five times. Our study revealed that the novel magnetic NAD kinase catalyst possessed favorable properties for magnetic manipulation and NADP production.

Reputation and Trust Mathematical Approach for Wireless Sensor Networks

Haiguang Chen,Gangfeng Gu,Huafeng Wu,Chuanshan Gao 보안공학연구지원센터 2007 International Journal of Multimedia and Ubiquitous Vol.2 No.3

In Wireless Sensor Networks (WSNs), these sensor nodes cooperate with each other to form a network without using any infrastructure. WSNs has a wide application. But the security of WSNs is still an important issue. Some existing approaches mainly rely on cryptography to ensure data authentication and integrity. These approaches only address part of the problem of security in WSNs. However, these approaches are not sufficient for the unique characteristics and novel misbehaviors encountered in WSNs. Recently, the use of reputation systems has become an important mechanism in WSNs. In this paper we propose a reputation and trust mathematical framework for WSNs which borrows tools from probability, statistics and mathematics analysis. We have suggested a new term certainty used in trust system and we argued that the positive or negative outcomes for a certain event is not enough information to make a decision in WSNs. We build up a reputation space and trust space in WSNs, and define a transformation from reputation space to trust space. Finally, we discuss some important properties of them and provide a basement in the trust and reputation for future research in WSNs. And we point out some open problems in reputation and trust system in WSNs.

Bagasse as functional fillers to improve and control biodegradability of soy oil-based rigid polyurethane foams

Zengcheng Yu,Yuqin Xiao,Huafeng Tian,Shilin Liu,Jian Zeng,Xiaogang Luo 한국화학공학회 2019 Korean Journal of Chemical Engineering Vol.36 No.10

Using agricultural wastes (bagasse) and polyol derived from soy oil as raw materials to develop biodegradable rigid polyurethane foams (RPUFs) is beneficial to reduce the dependence on petroleum resources and promote the sustainable socioeconomic and environmental development. This study focuses on bagasse as a functional filler to improve and control the mechanical properties and biodegradability of the RPUFs. With the increasing levels of bagasse content, the density and mechanical properties of RPUFs increase. The biodegradation of RPUFs has a greater enhancement compared to the foam without bagasse, and all bio-foams have excellent thermal insulation properties. All changes in foam performance are due to the fact that the active hydroxyl groups on bagasse react with excess isocyanate to form urethane, which affects the structure of RPUFs. In this study, scientific design and molecular regulation theory were applied to improve the utilization value of bagasse and develop high-performance biodegradable RPUFs for thermal insulation materials

Repair of flange damage steel-concrete composite girders using CFRP sheets

Lianguang Wang,Wenyu Hou,Huafeng Han,Junhua Huo 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.55 No.3

Damaged steel-concrete composite girders can be repaired and retrofitted by epoxy-bonded carbon fiber-reinforced polymer (CFRP) sheets to the critical areas of tension flanges. This paper presents the results of a study on the behavior of damaged steel-concrete composite girders repaired with CFRP sheets under static loading. A total of seven composite girders made of I20A steel sections and 80mm-thick by 900mm-wide concrete slabs were prepared and tested. CFRP sheets and prestressed CFRP sheets were used to repair the specimens. The specimens lost the cross-sectional area of their tension flanges with 30%, 50% and 100%. The results showed that CFRP sheets had no significant effect on the yield loads of strengthened composite girders, but had significant effect on the ultimate loads. The yield loads, elastic stiffness, and ultimate bearing capacities of strengthened composite girders had been changed as a result of prestressed CFRP sheets, the utilization ratio of CFRP sheets could be effectively improved by applying prestress to CFRP sheets. Both the yield loads and ultimate bearing capacities had been changed as a result of steel beam’s flange damage level and CFRP sheets could cover the girders’ shortage of bearing capacity with 30% and 50% flange damage, respectively.

Management of the energy harvesting for MEMS/NEMS via newmark current method

Shang, Kun,Shan, Huafeng,Alkhalaf, Salem,Marzouki, Riadh,Khadimallah, Mohamed Amine Techno-Press 2022 Advances in nano research Vol.12 No.6

The free and forced vibration in addition to electric energy harvesting of a piezoelectric disk resting on two-parameter foundation modeled by modified couple stress as well as Kirchhoff plate theory is probed. The governing equations and boundary conditions are obtained using Hamilton's principle. Then, the free and forced vibration are solved using numerical solutions, generalized differential quadrature method (GDQM) and Newmark-beta method. The forced vibration is resulted from a base excitation load. Also, the possible voltage which can be harvested from this system is obtained using generalized integral quadrature method. The validity of the formulation and solution procedure is confirmed using a compassion study. The impact of parameters such as length effect, inner to outer radius ratio, and foundations parameters on the free and forced vibration as well as energy harvesting is investigated in detail. This paper can be a basis for future studies in the area of piezoelectric harvesters in small scales.